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Financial Highlights (Tables) | 3 Months Ended
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Mar. 31, 2015
Financial Highlights [Abstract] |
Per Unit Performance Data and Other Supplemental Financial Data | The following table presents per share performance data and other supplemental financial data for the three months ended March 31, 2015 and 2014 for the shareholders. This information has been derived from information presented in the condensed financial statements.
|  | For the three months ended |  |  | For the three months ended |
|  | March 31, 2015 |  |  | March 31, 2014 |
|  | (Unaudited) |  |  | (Unaudited) |
Per Share Operating Performance: |  |  |  |  |  |  |  |
Net asset value, beginning of period |  | $ | 26.59 |  |  | $ | 42.83 |
Total income (loss) |  |  | (2.58) |  |  |  | 1.38 |
Total expenses |  |  | (0.05) |  |  |  | (0.11) |
Net increase (decrease) in net asset value |  |  | (2.63) |  |  |  | 1.27 |
Net asset value, end of period |  | $ | 23.96 |  |  | $ | 44.10 |
Total Return |  |  | (9.89) | % |  |  | 2.97 | %
Ratios to Average Net Assets |  |  |  |  |  |  |  |
Total income (loss) |  |  | (8.12) | % |  |  | 2.80 | %
Expenses excluding management fees* |  |  | 0.21 | % |  |  | 0.41 | %
Management fees* |  |  | 0.60 | % |  |  | 0.60 | %
Net income (loss) |  |  | (8.32) | % |  |  | 2.55 | %
* Annualized

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